I am a happy owner of this powerful amp driving my stacked Quad ESL 57 without any problem!I am considering the purchase of a second one to run in mono mode to gain power or to allow them to get margin to accept “forte” without distortion.The question is : what about very low Z (less than 2 Ohms) at high frequencies of 2 esl57 in parallel for the ZEN 84CS ?You mean that in series the two opt will see half the speaker load…